Undershirt with underarm gusset



FIG. 1 is a perspective view of the undershirt with underarm gusset showing the new design positioned on a body;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a back elevational view thereof;

FIG. 4 is a right side elevational view thereof;

FIG. 5 is a left side elevational view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken line portions of the drawings depict environmental subject matter only and form no part of the claimed design. 

CLAIM The ornamental design for an undershirt with an underarm gusset, as shown and described. 